1. Field of the Invention
The present invention relates to a variable optical-property element such as a variable focal-length lens, a variable focal-length diffraction optical element, a variable deflection-angle prism, or a variable focal-length mirror, and to an imaging optical system used in an optical apparatus, such as spectacles, a video projector, a digital camera, a TV camera, an endoscope, a telescope, or a camera finder, having an optical system including the variable optical-property element.
2. Description of Related Art
Conventional lenses have been manufactured by polishing glass. The focal length cannot be varied by the lens itself, and thus the mechanical structure of an optical system becomes complicated, for example, because a lens unit must be moved along the optical axis for focusing or zooming of a camera, or for a change of the magnification of the optical system.
Since a motor or the like is used for moving a part of the lens unit, this conventional practice has disadvantages that power consumption is large, noise is produced, response time is long, and much time is required for moving lenses.
For shake prevention as well, mechanical movement of the lenses by a motor or a solenoid causes defects such as a large power consumption and a complicate mechanical structure, resulting in a high cost.
An endoscope is one of optical apparatuses provided with imaging optical systems. Since the endoscope is used in such a way that it is inserted into a human body, a finer imaging optical system is required. Thus, it is very difficult to incorporate a focusing mechanism in the endoscope, and most of the optical systems of conventional endoscopes have constant focal lengths.
It is, therefore, a primary object of the present invention to provide an imaging optical system which is capable of performing focusing, irrespective of its small diameter and size, in an optical system of an endoscope, a monitoring camera, or a digital camera.
It is another object of the present invention to provide an imaging optical system which can be utilized for a robot""s eye, a cellular phone with an imaging function, a doorscope camera, a vehicle mounted camera, etc.
In order to achieve the above objects, the imaging optical system according to the present invention uses a deformable mirror, and is configured to perform focusing upon satisfying a condition, 50xc2x0 less than 2xcfx89 less than 175xc2x0, where xcfx89 is a horizontal half angle of view.
The imaging optical system according to the present invention uses a plurality of deformable mirrors to perform focusing.
The imaging optical system according to the present invention is constructed so that when focusing is performed, at least one deformable mirror has the shape of a free-formed surface in a certain state.
These and other objects as well as the feature and advantages of the present invention will become apparent from the following detailed description of the preferred embodiments when taken in conjunction with the accompanying drawings.